The present invention concerns wrist watches having a bracelet attached to the watch casing by hinges.
The term "hinge" is used to denote a pivot connection between two components and comprising at least one first element fixed to one of the components, at least one second element fixed to the other component, and at least one third element forming a pivot member.
French Pat. No. 2 251 291 discloses such a wrist watch, wherein the hinges are each formed by an element which is fixed to the casing of the watch, and two elements which are fixed to the bracelet and which are spaced from each other, these two elements flanking the element which is fixed to the casing. A pivot pin passes through all three elements, thereby defining a pivotal axis.
Thus, in the known construction, each hinge comprises only a single element which is fixed with respect to the watch casing, that element taking up the space between the two elements which are fixed to the bracelet. The pivot pin subjects the hinge element which is fixed with respect to the watch casing not only to tensile stresses which are at right angles to the axis of the pin, but also to twisting stresses which are centered at the middle of the pin. Accordingly, this known construction cannot be applied to watch casings of plastics material, as plastics material generally has poor strength against twisting stresses.
In addition, Swiss Pat. No. 405 170 describes a wrist watch in which the bracelet is formed by a plurality of rigid elements, probably of metal, which are each held in contact with an adjoining rigid element, and non-rigidly connected to the latter. The end elements of the bracelet, which are adjacent to the watch casing, are welded to the casing and are attached to the adjacent bracelet elements by means of a pin. Such a construction, which therefore does not use hinges as defined hereinbefore, is also such that it cannot be applied to a casing of plastics material. In fact, the end elements of the bracelet, which are welded to the watch casing, are subjected to mechanical twisting stresses by the immediately adjoining bracelet elements to which they are non-rigidly connected and with which they are held in contact.